1. Field of the Invention
This invention concerns internal combustion engines and more particularly fuel delivery systems for internal combustion engines which involve the induction of air-fuel mixtures into the engine.
2. Background Discussion
In conventional internal combustion engines of the carbureted type, liquid fuel such as gasoline is partially vaporized and mixed with air to form a fuel-air charge, which is inducted into the engine combustion chamber via the intake manifold. Conventional carburetion has never successfully produced a pure vaporized fuel-air mixture but rather has produced a mixture in the intake manifold of air, vaporized fuel and atomized fuel comprised of liquid droplets entrained or suspended in the flow of the mixture into the engine. Complete vaporization typically does not take place until the mixture has been inducted into the engine cylinders (in a piston engine). This lack of complete vaporization by the carburetor leads to increased carburetor complexity, less efficient engine operation and other operating disadvantages such as carbon build up in the engine etc. due to too rich mixtures being burned in the engine cylinders.
These disadvantages accrue in part from the increased inertia of the fuel in the mixture, i.e., at increased power demands, raw or liquid fuel must be injected into the air stream to quickly increase the amount of fuel in the charge. Such liquid fuel produces overly rich relatively wasteful mixtures which are inducted into the cylinders.
In addition, this requires the added complexity of the accelerator pumps normally incorporated in these carburetors.
The difficulty in achieving proper flow within the intake manifold is also rendered much greater since the inertia of the atomized particles has a tendency to create separation of the atomized fuel from the air flow at bends within the intake manifold and to create too rich or too lean fuel-air proportions at differing points within the intake manifold due to the redistribution of the atomized particles in the air stream. For example, at bends in the intake manifold, the air stream at the outer end of the bend tends to receive a greater proportion of the entrained atomized fuel particles, while those nearer the interior side of the bends receives less fuel. If such bends involve the division of flow to the various cylinders, then the individual cylinders may receive too rich or too lean mixtures, respectively. This then requires the engine to operate at either too rich a mixture overall to insure that all cylinders get an adequately rich mixture or that some cylinders will run too lean increasing temperatures and causing valve burning due to the presence of excess oxygen in the charge.
Liquid fuel may also accumulate within the intake manifold passages due to condensation on the walls and collection of the atomized particles at the outside of the bends of the intake manifold. Since the condensed particles tend to be the heavier molecular weight constituents which are more difficult to vaporize, the condensed or collected vaporized particles may be difficult to revaporize and may have a tendency to form a residue within the intake manifold increasing the restriction flow on the air through the intake manifold and reducing the volumetric efficiency of the engine.
These conditions are particularly aggravated when the engine is cold, prior to the warming of the intake manifold by the various manifold warming devices or the recirculation of exhaust gases. Since a great proportion of driving takes place under cold engine conditions, this has a substantially negative impact on the performance of the engine.
These negative characteristics of the nonvaporized condition of the fuel-air charge downstream of the carburetor have long been recognized but are of more particular concern under present day conditions in which both emissions and fuel economy have become critical design considerations due to the relative high cost of gasoline and governmental regulation of both passenger car fuel economy and emission levels.
It has also long been recognized that heating of the inducted air charge to improve vaporization is possible, but entails a penalty on the efficiency of the engine which would nullify the improvement in engine efficiency and performance characteristics.
This penalty involves a decreased volumetric efficiency of the engine, i.e., the air becoming relatively rarefied as it is heated, less mass is inducted into the cylinders producing a reduced volumetric efficiency and therefore an overall reduced thermodynamic efficiency of the engine.
In addition, overheating of the inducted air may lead to an increased tendency to knock.
Hot air vaporization systems have also heretofore been proposed in which the vaporization is aided by means of a relatively small quantity of auxiliary hot heated air being passed into the intake manifold. Examples of such systems are found in U.S. Pat. Nos. 1,256,976 to Brock; 1,241,155 to Sevigny; 1,420,615 to Webber; 1,364,543 to Callo; 1,565,181 to Manning; 1,143,331 to Strange and Hefrien; and 1,157,189 to Schneider.
These systems generally involve the heating of a small quantity of air by means of the exhaust manifold and the induction of the heated air into the intake manifold, via a tube connection to the intake manifold. These systems have not heretofore been successful in producing the hot air vaporization effectively. That is, to substantially cause total vaporization of the fuel in the air charge without producing performance penalties such as excessively leaning the mixture, overheating of the air in the charge, etc.
It has been determined by the present inventors that the mode of introducing this air into the intake manifold is critical in achieving high efficiency in the hot air vaporization process. That is, if the hot air can be introduced at the proper temperature and flow rate of a given engine configuration, and in the proper manner, complete vaporization can be achieved such as to obviate the performance disadvantages described above resulting from incomplete vaporization without entailing substantially the penalties of the introducing of hot air into the fuel-air mixture.
It is accordingly an object of the present invention to provide an arrangement for producing auxiliary hot air vaporization in an internal combustion engine involving the formation of a fuel-air charge prior to induction into the engine in which maximum fuel efficiency of the hot air induction process is achieved.
Of course, as with any engine component, relative simplicity and troublefree and maintenance free performance is of considerable importance. Most of the systems described in the above patents require manual adjustment and/or control components increasing the complexity of the system such that many are not suited to modern day automotive applications.
It is therefore another object of the present invention to produce such a hot air vaporization system in which maintenance is kept to an absolute minimum and the simplicity of the system lends itself to mass application to the engines of automotive vehicles.